JP2002064067A - Conditioned chamber for improving chemical vapor deposition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a process for conditioning a CVD chamber between deposition steps by using fluorine-containing gas, removing fluorine residues remaining in a chamber, and at the same time ensuring that fine particles remaining in a chamber do not fall on a substrate. SOLUTION: A multi-step process is used to adjust a chemical vapor deposition chamber after cleaning and between successive depositions, by removing fluorine residues from the chamber with a hydrogen plasma, and subsequently depositing a solid compound in the chamber to encapsulate any particles remaining in the chamber.

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates generally to chemical vapor deposition (CV).
D) Regarding processing. More particularly, the present invention relates to conditioning a CVD chamber after chamber cleaning and before a subsequent CVD process.

[0002]

BACKGROUND OF THE INVENTION CVD is widely used in the semiconductor industry to deposit various types of films on substrates, such as intrinsic or doped amorphous silicon, silicon oxide, silicon nitride, silicon oxynitride, and the like. New semiconductor C
VD processing is usually performed by heating a precursor gas in a vacuum chamber to dissociate and react to form a desired film. A plasma can be generated from a precursor gas in the chamber during deposition to deposit the film at a relatively high deposition rate at low temperatures. Such a process is known as a plasma enhanced chemical vapor deposition process, or PECVD.

An elaborate CVD chamber is made of aluminum and contains a substrate support to be processed and an inlet for the required precursor gas. If a plasma is used, the gas inlet and / or the substrate support is connected to a power source, such as an RF power source. A vacuum pump is also connected to the chamber to control the pressure in the chamber and to remove various gases and particulates generated during the deposition.

As semiconductor devices on substrates become smaller and come closer together, particulate matter in the chamber must be minimized. During the deposition process, the deposited film not only deposits on the substrate, but also on the walls in the chamber and various fixtures, such as shields, substrate supports, and the like. In the subsequent deposition, the film on the wall may be cracked or peeled off, and contaminant particles may fall on the substrate. This causes problems or damage to specific devices on the substrate. As individual devices or dies are cut from the silicon wafer, damaged devices such as, for example, transistors can be disposed of.

Similarly, when processing large glass substrates to form thin film transistors used as computer screens and the like, up to one million transistors are formed on a single substrate. The computer screen does not work when damaged by fine particles,
The presence of contaminants in the processing chamber is severe.

Accordingly, the CVD chamber must be periodically cleaned to remove particulate matter between depositions. Cleaning is often performed by sending an etching gas, particularly a fluorine-containing gas such as nitrogen trifluoride, to the chamber. Next, a plasma is generated from the fluorine-containing gas and reacted with a coating from a previous deposition on the chamber walls, i.e., a coating such as amorphous silicon, silicon oxide, silicon nitride, or particulate matter in the chamber to form gaseous fluorine. A contained product can be formed and pumped out by a chamber exhaust system. This is usually driven by a nitrogen purge.

However, it has been found that fluorine residues still remain in the chamber after this cleaning step, and more importantly, that all particulate matter has not been removed from the chamber. Fluorine residues can adversely affect the quality of the next deposited film, particularly the quality of amorphous silicon on a silicon nitride film, and shift the threshold voltage of devices made with that film. The presence of particulate matter can damage devices on the substrate.

Thus, conditioning the CVD chamber between deposition steps using a fluorine-containing gas, and then removing any fluorine residue remaining in the chamber,
At the same time, there is a need for a process that can ensure that particulate matter remaining in the chamber does not fall on the substrate.

[0009]

SUMMARY OF THE INVENTION This is done after cleaning unwanted deposits in the chamber with a fluorine-containing gas to remove fluorine residues from the chamber and reduce the number of particles in the chamber that can fall onto subsequent processing substrates. ,
We have found a multi-step conditioning process for a CVD chamber.

[0010] In a preceding cleaning step, the fluorine is sent to the chamber where it reacts with unwanted deposits and particles. In the first adjusting step of the present invention, a plasma is generated from hydrogen in the chamber and reacted with the fluorine residue remaining in the chamber. These are wiped out. In a second conditioning step, a plasma is generated from the deposition gas mixture to form a solid compound layer on the walls and fixtures of the chamber, effectively encapsulating particulate matter remaining on the interior surfaces of the chamber.

[0011] The deposition gas mixture can be silane and optionally added co-reactants, and is capable of forming a solid silicon compound such as silicon oxide or silicon nitride in the chamber. Alternatively, the deposition gas mixture may be tetraethoxysilane (TEOS) and oxygen, capable of forming a silicon oxide compound. Generally, the deposition gas mixture used in the conditioning step uses a portion of the same gas used to deposit the film on the substrate.

DETAILED DESCRIPTION OF THE INVENTION Robertson et al., US Pat. No. 5,366,5
No. 85 discloses a PECVD chamber suitable for processing large area glass plates, the disclosure of which is incorporated herein. Here, FIG. 1 will be described. The vacuum chamber 113 surrounded by the reactor housing 112 includes a hinge lid. The gas manifold 132 is positioned parallel on the susceptor 116 on which the substrate is mounted during processing. Gas manifold 13
2 includes a face plate 192 having a plurality of orifices 193 for supplying a process gas and a purge gas. The RF power supply 128 generates a plasma from the supplied gas.

A set of ceramic liners 120, 121, 122 adjacent the housing 112 insulate the metal walls of the housing 112 so that no arcing occurs between the housing 112 and the susceptor 116 during plasma processing. These ceramic liners 12, 121, 122 can also withstand fluorine-containing etch cleaning gases. The ceramic ring 123 is also coupled to the face plate 192 such that the face plate 192 is electrically insulated. These ceramic components also repel the plasma, thus helping to confine the process plasma near the substrate and helping to reduce the amount of deposits that accumulate on the walls of the housing 112.

After the last substrate on which the layers are to be deposited is removed from the chamber, a standard fluorine-containing gas cleaning is first performed in the chamber in a conventional manner. An 800 sccm flow of nitrogen trifluoride was set with the gas injection valve wide open, the pressure in the chamber was 200 mTorr, and the susceptor-gas manifold spacing was 1600 mils. 1600 watts of RF power is applied to the gas manifold to generate a plasma. For each 2000 Å amorphous silicon film previously deposited in the chamber, the cleaning plasma was continued for about 1 minute. For each 4000 Å silicon nitride film previously deposited on the substrate in the chamber, the cleaning plasma was continued for about an additional minute.

The following two-step adjustment process is based on the above C
It is used for removing particles of fluorine remaining after the VD chamber clean step and depositing a thin film of an inert solid compound on walls and fittings in the chamber to encapsulate particles.

As an example of the process of the present invention, in the first conditioning step, 1200 sccm of hydrogen is introduced into the chamber.
A hydrogen plasma was generated in the chamber by feeding for 300 seconds and generating plasma using 300 watts of power. The hydrogen plasma reacts with the fluorine present in the chamber to produce HF that can be easily removed by the chamber exhaust system. The chamber was maintained at the temperature used for subsequent deposition and at a pressure of 1.2 torr. The spacing between the substrate support and the gas manifold was 1462 mil.

In the second conditioning step, a thin film of silicon nitride was deposited under the same spacing, temperature and pressure conditions, but the power was increased to 800 watts and the gas was changed. A silicon nitride film was deposited by sending 100 sccm of silane, 500 sccm of ammonia and 3500 sccm of nitrogen to the chamber for 30 seconds.

Thus, the total time required to condition the chamber for a subsequent deposition process is only about one minute. The thin film of silicon nitride covers the walls and fixtures of the chamber, thus encapsulating and sealing the particles remaining in the chamber after the cleaning step, so that there is no chance of particles falling on the substrate being processed. The deposited silicon nitride layer also reduces outgassing of the wall material,
The remaining fluorine-containing material from the chamber is further reduced.

The above two-step conditioning process is used with a standard cleaning process that includes cleaning stabilization, plasma cleaning with a fluorine-containing gas, followed by a nitrogen purge. After the hydrogen plasma treatment and silicon compound deposition of the conditioning process, the chamber may be purged with nitrogen.

The above process is preferred because it removes fluorine-containing residues and reduces the number of particles in the chamber while minimizing the reduction in system throughput. An alternative single-step adjustment process using the same amount of processing time has been attempted, but is not as effective as this process. A single 60 second silicon nitride deposition process is effective in reducing particles but not in reducing fluorine residues. This process also produces thick wall deposits that must be etched in subsequent cleaning steps. A 50 second single step to generate hydrogen plasma is effective in reducing fluorine residues but not in reducing particles. A 60-second single step of amorphous silicon deposition formed by adding silane to a hydrogen plasma process is effective in reducing fluorine residues due to the large generation of hydrogen atoms. However, particle reduction is not as effective as silicon nitride deposition. Furthermore, the amorphous silicon deposition needs to be removed in a subsequent cleaning step.

An alternative two-step conditioning process using the same amount of processing time is also not effective. Adding 30 seconds of silicon nitride deposition to 30 seconds of amorphous silicon deposition,
Effective for reducing fluorine residues and particles. However, the added amorphous silicon wall deposits need to be removed in a subsequent cleaning step.
The above multi-step cleaning and conditioning process has been used with the stabilization of a conventional reaction chamber between cleaning steps, and a nitrogen purge has
It may be used after the fluorine cleaning step and after the silicon nitride deposition step in preparation for VD processing.

FIG. 2 is a flow chart showing a preferred step sequence of the present CVD chamber cleaning process and the adjustment process. First, the plasma CVD chamber is cleaned with a fluorine-containing gas, hydrogen plasma is generated in the chamber to remove fluorine residues, a plasma of a silicon compound precursor gas is generated, and a solid silicon compound is deposited inside the chamber. After purging the chamber with an inert gas,
The substrate on which the material is to be deposited is inserted into the chamber.

Although the process has been described by way of specific examples, it will be apparent to those skilled in the art that various changes in gases, reaction conditions, etc., can be made and are meant to be included herein. There will be.

Additionally, while specific CVD chambers have been described herein, many CVD chambers are commercially available and can be cleaned and adjusted according to the process.
The present invention should be limited only by the appended claims.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a PECVD chamber used to deposit thin films on large area glass substrates.

FIG. 2 is a flowchart showing the steps of a preferred process of the present invention.

[Explanation of symbols]

112 ... reactor housing, 113 ... vacuum chamber,
116: susceptor, 120, 121, 122: ceramic liner, 123: ceramic ring, 128: RF power supply,
192: face plate, 193: orifice, 132: gas manifold.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Robert Robertson, Inventor Ravenwood Drive, Saratoga, California, United States 18519 (72) Inventor Mike Collac United States, California, San Francisco, Nineteenth Avenue 1369 (72) Inventor, Angela Lee United States of America, California, San Jose, Castle Glen Avenue 5476 (72) Inventor Takako Takehara United States of America, California, Hayward, Colony View Place 2811 (72) Inventor Jeff Fen United States of America, California, Saratoga, Seagull Way 20225 (72) Inventor Curenuance Canyon View Drive, Saratoga, California, United States 21090 (72) Inventor Cam Row United States, California, Union City, Riviera Drive 461 F-term (reference) 4K030 AA06 AA13 AA18 BA40 CA04 DA06 FA03 JA05 JA09 JA11 JA16 KA49 LA15 5F045 AA08 AB33 AC01 AC02 AC15 EB03 EB06 EC05 EE13 EH13

Claims (19)

[Claims] A) introducing a halogen-containing gas into a chamber and reacting the gas with a deposit on a surface of the chamber to form a halogen residue; b) introducing hydrogen into the chamber to form a hydrogen residue. Generating a plasma and reacting the hydrogen plasma with the halogen residue to form a reaction product; c) removing the reaction product formed by reacting the hydrogen plasma with the halogen residue; d) introducing a deposition gas mixture into the chamber and depositing the deposition gas to encapsulate the reaction product. 2. The method of claim 1, wherein said halogen containing gas is a fluorine containing gas. 3. The method of claim 1 further comprising the step of extruding said halogen gas from said chamber using nitrogen gas. 4. The hydrogen plasma of step b) comprises:
The method of claim 1, wherein the method is produced by delivering 00 sccm of hydrogen to the chamber for about 30 seconds. 5. The method of claim 1, wherein the hydrogen plasma of step b) is about
5. The method of claim 4, wherein the method is generated using about 300 watts of power at a pressure of 1.2 torr. 6. The method of claim 1, wherein said deposition gas mixture comprises silane, said silane forming a solid silicon compound layer on an interior surface of said chamber. 7. The method of claim 6, wherein said solid silicon layer is silicon oxide. 8. The method of claim 6, further comprising the step of adding a nitrogen-containing gas to said deposition gas mixture in step c). 9. The method of claim 6, wherein said solid silicon layer comprises a silicon nitride layer. 10. The method of claim 9, wherein said silicon nitride layer is formed from a gas mixture comprising about 100 sccm silane, about 500 sccm ammonia, and about 3500 sccm nitrogen gas. 11. The method of claim 9, wherein said silicon nitride layer is formed by exposing said chamber to said deposition gas for about 30 seconds. 12. The method of claim 9, wherein said silicon nitride is deposited at about 800 watts. 13. The method of claim 1, wherein said deposition gas mixture comprises tetraethoxysilane, said silane forming a solid silicon oxide compound layer on an interior surface of said chamber. 14. The method of claim 1, wherein said halogen containing gas comprises nitrogen trifluoride. 15. A method for conditioning a chemical vapor deposition (CVD) processing chamber after cleaning the chamber, the method comprising: a) generating a hydrogen plasma in a chemical growth chamber; Reacting with contaminant molecules in the chamber to form a reaction product; and b) depositing a silane compound layer in a manner to encapsulate the reaction product in the chamber. 16. The method of claim 15, wherein said silane compound is deposited using a gas comprising tetraethoxysilane. 17. The method of claim 15, wherein a hydrogen plasma is created in the chamber by introducing hydrogen gas at a power of about 300 watts. 18. The method of claim 1, wherein said silane compound is deposited using a gas comprising silicon nitride. 19. The method of claim 18, wherein said silicon nitride is deposited at about 800 watts.